Deburring apparatus in which material to be removed from a workpiece is oxidized or combusted under high thermal and pressure loading is known. A heat and pressure shock is generated by explosively combusting a mixture of oxygen and a combustion gas. The combustion gas may be hydrogen, natural gas, methane, or the like. It is necessary to compress the mixture of gas prior to ignition in order to liberate the necessary energy to remove burrs and similar imperfections from a workpiece. Generally, metering cylinders and gas injection cylinders have been used, in which a piston provides a predetermined quantity of gas, and compresses it, and propels the so compressed gas into the combustion chamber. Mixing and ignition of the combustion gas and the oxygen can be carried out in a separate mixing structure, typically retained within a metal block. Such a mixing block may include a housing in which the mixing chamber as well as an ignition arrangement are located. Such a mixing chamber is then connected over comparatively long ducts, forming gas supply ducts with the gas supply connections to the mixing block. The long gas supply ducts are provided in order to protect the valves which are located between the mixing block and the metering arrangement so that, upon ignition of the highly compressed gases, the valves are not damaged. Combustion temperatures of the gases are in a range of between 2500.degree. C. to 3500.degree. C. The pressure which may occur upon filling of the combustion chamber of the oxygen and combustion gas mixture is in the order of 40 bars.
Apparatus for thermal deburring usually uses a workpiece support plate which forms the lower closing portion of the deburring chamber. A bell-like structure is then placed on the plate, and sealed thereagainst, to define the deburring chamber therein. Sealing between the deburring bell and the closing plate is effected by high pressure, for example by a hydraulically operated structure, e.g. the lever, for example, a double-arm, bent-arm lever. The combustion gas and oxygen mixture is supplied over a mixing chamber in a mixing block.
It has been found that such apparatus, in spite of all precautions taken, results in degradation of the valves since the burning oxygen--fuel mixture, upon ignition, will reach the gas supply valves, separating the gas from the metering apparatus. The high temperatures and pressure occurring during combustion additionally cause wear and degradation of the igniter opening or igniter bore, and the bores and ducts which lead the gases to the deburring chamber.